package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func configure(scanner *bufio.Scanner) {
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
}
func getNextString(scanner *bufio.Scanner) string {
	scanned := scanner.Scan()
	if !scanned {
		panic("scan failed")
	}
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	extra := 0
	if os.Getenv("I") == "IronMan" {
		fp, _ = os.Open(os.Getenv("END_GAME"))
		extra = 100
	}
	scanner := bufio.NewScanner(fp)
	configure(scanner)
	writer := bufio.NewWriter(wfp)
	defer func() {
		r := recover()
		if r != nil {
			fmt.Fprintln(writer, r)
		}
		writer.Flush()
	}()
	solve(scanner, writer)
	for i := 0; i < extra; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	n := getNextInt(scanner)
	d := newDeque(n + 5)
	if n == 1 {
		fmt.Fprintln(writer, 0)
		return
	}
	l := 1
	r := n
	d.pushBack(l)
	l++
	for i := 1; i < n; i++ {
		if i%2 == 0 {
			if d.at(0) < d.at(i-1) {
				d.pushBack(l)
				l++
				continue
			}
			d.pushFront(l)
			l++
			continue
		}
		if d.at(0) < d.at(i-1) {
			d.pushFront(r)
			r--
			continue
		}
		d.pushBack(r)
		r--
	}
	var ans int64
	for i := 0; i < n; i++ {
		ans += int64(d.at(i)) * int64(d.at((i+1)%n))
	}
	fmt.Fprintln(writer, ans)
}

type deque struct {
	list       []int
	l, r, size int
}

func newDeque(size int) deque {
	return deque{
		list: make([]int, size),
		l:    0,
		r:    0,
		size: size,
	}
}
func (deq *deque) index(i int) int {
	if i < 0 {
		i += deq.size
	}
	if i >= deq.size {
		i -= deq.size
	}
	return i
}
func (deq *deque) at(i int) int {
	return deq.list[deq.index(deq.l+i)]
}
func (deq *deque) pushBack(x int) {
	deq.list[deq.r] = x
	deq.r = deq.index(deq.r + 1)
}
func (deq *deque) pushFront(x int) {
	deq.l = deq.index(deq.l - 1)
	deq.list[deq.l] = x
}
func (deq *deque) popBack() {
	deq.r = deq.index(deq.r - 1)
}
func (deq *deque) popFront() {
	deq.l = deq.index(deq.l + 1)
}